Emails are still the most common delivery method for malicious files, according to Check Point’s Cyber Security Report for 2024.
“Email-based attacks continue to be the dominant initial infection vector,” the report says.
“Eighty-eight percent of all malicious file deliveries occur through email, with the remainder downloaded directly from the internet. Threat actors have adapted to email protection strategies and are exploring innovative delivery techniques. Following Microsoft’s restrictions on Office VBA macros in files from external sources denoted with the Mark-of-the-Web (MotW), there was a sharp decrease in the prevalence of malicious Office files, from nearly 50% in 2022 to 2% in 2023. Notable alternative attack vectors include HTML files and various archive file types.”
Notably, the researchers observed a spike in the use of HTML files to deliver malicious content.
“In particular, the exploitation of HTML files saw a significant uptick,” the researchers write. “HTML files comprise 69% of all malicious file attachments. Threat actors use HTML files in several ways. They are used in phishing schemes to imitate legitimate website login pages and steal user credentials. They can include malicious JavaScripts or exploits to unpatched browser and browser-plugins. As demonstrated in recent CP<R> research, these tactics are not limited to low-level criminals but are also utilized by advanced APT actors. Other uses of HTML include HTML smuggling, or auto download for executables and redirections to other malicious URLs. Legitimate use cases of email-delivered HTML are unusual and therefore organizations should consider implementing restrictions.”
Attackers are also using password-protected archives to avoid detection by security filters.
“Utilization of various archive files has also been on the rise,” Check Point says. “The contents of password-protected archives are hidden from many security services, thus forming an effective attack vector. Other formats like .img and .iso depend on the software used for their extraction to propagate the MotW functionality, which is used to prevent malicious attempts. While Microsoft has fixed this feature, other providers like 7-zip have opt-in policies, thus decreasing the effectiveness of the MotW protection mechanism.”
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